The purpose of this multi-disciplinary Center is to explore the neural bases of language and cognitive development from 7-18 years of age, combining cross-sectional and longitudinal behavioral methods with neural imaging (event-related brain potentials (ERP); functional magnetic resonance imaging (fMRI) to study normal and abnormal brain development, and the alternative forms of brain organization that can emerge under pathological conditions, and the alternative forms of brain organization that can emerge under pathological conditions. Project A focuses on children with Language Impairment (LI); it examines the cognitive and neural correlates of LI, and test competing hypotheses about the processing deficits that underlie this disorder. Project B follows children with focal lesions (FL) to one side of the brain, acquired pre- or perinatally (before 6 months of ages); it will provide behavioral, fMRI and ERP evidence regarding the alternative forms of organization the underlie plastic reorganization in the plastic reorganization in this population. Project C compares Williams Syndrome (WMS), a rare form of mental retardation in which language is especially vulnerable. Project D is new, and constitutes an extension of Project 2 to study children with lesions of later onset in childhood, children with bilateral pathology, and children with slowly evolving lesions due to tumor; the purpose of this project is to increase our understanding of developmental and neurological limits on plasticity. Project E is new, a groundbreaking series of studies using fMRI, including BOLD activation studies of language, spatial processing and spatial attention, as well as perfusion studies of vascular organization. Project F continues our ERP studies of language, spatial cognition and basic auditory-visual processing in all populations. Core A handles administration, data base management, tracking and statistical consultation.. Core B is responsible for recruitment of controls, and handles screening, diagnosis and induction of all populations. Core C is a new joint behavioral testing facility that handles language and behavioral testing (excluding ERP and fMRI) for all populations, including language transcription.